An epidermoid cyst (Epidermal Inclusion cyst, Infundibular cyst), is a benign growth commonly found in the skin and typically appears on the face, neck or trunk, but can occur anywhere on the body. Another name used is “sebacous cyst” but this is actually an antiquated misnomer, and is not a term used by dermatologists.
They are also the most common type of cutaneous cysts. Epidermoid cysts result from the reproduction of epidermal cells within a confined space of the dermis. The pasty contents are mostly composed of macerated keratin (wet skin cells), which creates this “cheesy” consistency, and there can be a pungent odor. An epidermoid cyst may have no symptoms and are typically harmless.
Usually people seek removal because they don’t like the appearance of these bumps, or the cyst has ruptured or been inflamed or “infected” in the past. Rupture is associated with sudden redness, pain, swelling, and local heat, and can lead to abscess formation. Also, a history of inflammation, often increases scar tissue in the area, makes the cyst more firmly adherent to surrounding skin, and makes it more difficult to remove. Surgical excision is curative, but the complete cyst removal including the entire cyst sac and contents need to be removed to ensure that the cyst won’t reoccur.